Technical Field
The present invention relates to a sheet post-processing apparatus which temporarily stores image-formed sheets in a processing tray to perform post-processing such as binding processing and then stores in a stack tray.
Description of the Related Art
Generally, this type of sheet post-processing apparatus is widely used as an apparatus which is coupled to a sheet discharge outlet of an image formation apparatus, collates and stores discharged sheets on a processing tray to perform post-processing such as binding processing, folding processing, punching processing and stamping processing, and then stores the processed sheets (bunch) in a stack tray prepared on the downstream side.
Then, such a post-processing apparatus is known that a processing tray and a stack tray are arranged next to each other in a sheet discharge outlet of an image formation apparatus, a rear end portion of a sheet transported from the sheet discharge outlet is supported on the processing tray, a front end portion of the sheet is supported on the uppermost sheet on the stack tray, the sheet is thereby held with the front and rear partially supported, and that a bunch of sheets collated on the processing tray is subjected to binding processing with a staple apparatus (for example, see Japanese Patent Application Publication No. 2011-126620). Such a post-processing mechanism that bridge-supports a sheet transported from the sheet discharge outlet on the processing tray and the stack tray on the downstream side thereof is widely adopted because it is possible to miniaturize the apparatus.
In the apparatus in Japanese Patent Application Publication No. 2011-126620, a height difference is formed from the sheet discharge outlet to arrange the processing tray that supports the sheet rear end portion, and another height difference is formed on the downstream side of the processing tray to arrange the stack tray that supports the sheet front end portion. Then, a pair of right and left alignment device for supporting side edge portions of the sheet are provided above the stack tray to align the sheet in a post-processing position on the processing tray, the sheet is positioned in the processing position by a shifting the alignment device from retracted positions retracted from reference positions (center reference) to the reference positions (alignment positions), and sheets are subjected to post-processing on the processing tray. It is configured that after the post-processing, the alignment members are shifted to the side of the sheets, and that the sheets subjected to the post-processing are dropped into the stack tray to store.
In the post-processing apparatus for thus holding the sheet in the shape of a bridge in cooperation between the processing tray and the stack tray on the downstream side thereof, such a configuration is also known that alignment members are provided on both the processing tray and the stack tray (for example, see Japanese Patent Application Publication No. 2012-188194).